JP2005295239A - Radio transmitter, radio receiver, radio transmission method and radio reception method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio transmitter employing a radio communication preamble capable of properly performing A-D conversion by performing highly accurate AGC in receiving signals from a plurality of transmission antennas. <P>SOLUTION: A PLCP signal including a short preamble sequence 101, a first long preamble sequence 102, and signal fields 103, 104 which are sequentially transmitted from one antenna Tx1; a plurality of AGC preamble signals 105A to 105D each transmitted from a plurality of antennas Tx1 to Tx4 after transmitting PLCP signal; and a radio communication preamble signal having second long preamble signals 106A-109A, 106B-109B, 106C-109C and 106D-109D which are transmitted from antennas Tx1-Tx4, respectively, after AGC preambles 105A-105D are disposed before transmission data 110A-110D. The first signal field 103 includes a reserve bit 132 for previously notifying the transmission of the AGC preambles 105A-105D. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless transmission device, a wireless reception device, a wireless transmission method, and a wireless reception method that perform transmission and reception using a wireless packet including a specific preamble signal.

  The IEEE, an association of electrical and electronic engineers in the United States, is developing a wireless LAN standard called IEEE 802.11n aiming for a throughput of 100 Mbps or more. In IEEE 802.11n, there is a high possibility that a technique called MIMO (Multi Input Multi Output) using a plurality of antennas for a transmitter and a receiver will be adopted. IEEE 802.11n is required to coexist on the radio with the already standardized IEEE 802.11a standard. In MIMO technology, it is necessary to transmit a preamble, which is a known sequence, from a plurality of transmission antennas in order to measure a transmission path response from the plurality of transmission antennas to each reception antenna.

  According to the radio communication preamble signal proposed in Non-Patent Document 1, as shown in FIG. 9, a radio packet including a radio communication preamble signal is first transmitted from one transmission antenna Tx1 to time synchronization, frequency synchronization, and AGC. A short preamble sequence x01 to be used, a long preamble sequence x02 for channel response estimation, and a first signal field x03 including a field indicating the modulation scheme and length of the radio packet are transmitted. Subsequently, the second signal field x04 used in IEEE 802.11n is transmitted. Next, long preamble sequences x05, x06, and x07 for transmission channel response estimation are sequentially transmitted from the transmission antennas Tx2, Tx3, and Tx4. After the preamble signal transmission is thus completed, transmission data x08, x09, x10, and x11 are simultaneously transmitted from the plurality of transmission antennas Tx1, Tx2, Tx3, and Tx4.

The wireless communication preamble signal shown in FIG. 9 is the same as the wireless communication preamble signal of the IEEE 802.11a standard based on transmission from the single antenna Tx1 from the short preamble x01 to the first signal field x03. Accordingly, the wireless reception device based on the IEEE 802.11a standard that has received the wireless packet illustrated in FIG. 9 can recognize the received wireless packet as a packet based on the IEEE 802.11a standard. Therefore, the preamble signal for wireless communication shown in FIG. 9 enables IEEE 802.11n to coexist with the IEEE 802.11a standard on one wireless device.
Jan Boer and two others “Backwards compatibility”, [online], September 2003, IEEE LMSC, [searched September 15, 2003], Internet <URL: ftp: // ieee: wireless@ftp.802wirelessworld. com / 11/03 / 11-03-0714-00-000n-backwards-compatibility.ppt>

  Since demodulation processing of a reception signal in a wireless reception apparatus is generally performed by digital signal processing, an A / D converter that converts a reception signal obtained as an analog signal into a digital signal is prepared. The A / D converter has an allowable level range (hereinafter referred to as an input dynamic range) of an analog signal to be converted. Therefore, it is necessary to perform AGC (automatic gain adjustment) for adjusting the level of the received signal so as to be within the input dynamic range of the A / D converter.

  Since the transmission path response estimation using the long preamble described above is performed by digital signal processing, it is necessary to perform AGC using a signal before the long preamble. In the radio communication preamble signal shown in FIG. 9, AGC is performed using the short preamble x01 before the long preamble x02 transmitted from the transmission antenna Tx1 first. That is, the reception level of the short preamble x01 is measured, and AGC is performed so that the signal level is within the input dynamic range of the A / D converter. By performing AGC using the short preamble x01, it is possible to correctly receive the long preamble x02 and data transmitted from the transmission antenna Tx1.

  However, since nothing is transmitted before the long preambles x05, x06, x07 from the transmission antennas Tx2, Tx3, Tx4, AGC must be performed using the short preamble x01 transmitted from the transmission antenna Tx1. It is known that the reception levels of the signals transmitted from Tx1, Tx2, Tx3, and Tx4 are naturally different if the transmission antennas Tx1, Tx2, Tx3, and Tx4 are spatially separated.

  Therefore, when the radio reception apparatus receives the long preambles x05, x06, and x07 transmitted from the transmission antennas Tx2, Tx3, and Tx4, or when receiving the data signals x08 to x11 that are simultaneously transmitted from a plurality of antennas, the reception is performed. A phenomenon occurs in which the level greatly exceeds or falls below the level adjusted by AGC using the short preamble x01 transmitted from the antenna Tx1. When the reception level exceeds the upper limit of the input dynamic range of the A / D converter, the A / D converter causes a saturation phenomenon. When the reception level falls below the lower limit of the input dynamic range, a large quantization error occurs in the A / D converter. In any case, the A / D converter cannot perform appropriate conversion and adversely affects the processing after the A / D conversion.

  Further, as shown in FIG. 9, since data is transmitted from all the transmission antennas Tx1, Tx2, Tx3, and Tx4, the range of change of the reception level is further increased in the data portion. Therefore, the above-mentioned problems of saturation of the A / D converter and quantization error become remarkable, and the reception performance is greatly deteriorated.

  As described above, in the conventional technique, since AGC is performed using only the short preamble transmitted from the single antenna Tx1 on the receiving side, reception that occurs when receiving transmission signals from the other antennas Tx2, Tx3, and Tx4 is performed. Cannot cope with level fluctuations. Also, it cannot cope with fluctuations in the reception level when signals are transmitted simultaneously from the antennas Tx1, Tx2, Tx3, and Tx4.

  An object of the present invention is to provide a radio transmission apparatus that uses a radio communication preamble signal that performs high-accuracy AGC and appropriately performs A / D conversion when receiving signals from a plurality of transmission antennas, It is an object to provide a wireless reception device, a wireless transmission method, and a wireless reception method.

  According to a first aspect of the present invention, a plurality of antennas; a short preamble sequence, a first long preamble sequence, a first signal field, and a second signal field are transmitted using one of the plurality of antennas. Means for transmitting an AGC preamble using the plurality of antennas after transmitting the second signal field; and means for transmitting data using the plurality of antennas after transmitting the AGC preamble. The first signal field provides a radio transmission apparatus having a reserve bit for notifying transmission of the AGC preamble.

  According to a second aspect of the present invention, a plurality of antennas; a short preamble sequence, a first long preamble sequence, a first signal field, and a second signal field are transmitted using one of the plurality of antennas. Means for transmitting an AGC preamble using the plurality of antennas after transmitting the second signal field; and means for transmitting data using the plurality of antennas after transmitting the AGC preamble. The first signal field provides a radio transmission apparatus having a second signal field, an AGC preamble, and a reserve bit indicating that data is transmitted.

  According to a third aspect of the present invention, a plurality of antennas; a short preamble sequence, a first long preamble sequence, a first signal field, and a second signal field are sequentially transmitted using one of the plurality of antennas. Means for transmitting an AGC preamble using the plurality of antennas after transmitting the second signal field; and means for transmitting data using the plurality of antennas after transmitting the AGC preamble. The first signal field provides a radio transmission apparatus having a reserve bit indicating that the AGC preamble and data transmission are notified by using the plurality of antennas.

  According to a fourth aspect of the present invention, a short preamble sequence, a first long preamble sequence, a first signal field and a second signal field having reserved bits transmitted sequentially from one antenna, and after the second signal field. A receiving unit that receives a signal including a plurality of AGC preambles and data signals transmitted sequentially from a plurality of antennas to generate a received signal; a variable gain amplifier that amplifies the received signal; and triggers reception of the reserved bits And a gain control unit that controls the gain of the variable gain amplifier using the AGC preamble.

  According to a fifth aspect of the present invention, a short preamble sequence, a first long preamble sequence, a first signal field and a second signal field having reserve bits transmitted sequentially from one antenna, and after the second signal field. A reception unit that receives a signal including a plurality of AGC preambles and data signals transmitted sequentially from a plurality of antennas to generate a reception signal; a variable gain amplifier that amplifies the reception signal; and the AGC preamble There is provided a radio reception apparatus comprising: a gain control unit that controls a gain of the variable gain amplifier; and a start control unit that performs control to start a gain control operation of the gain control unit in response to reception of the reserve bit. .

  According to a sixth aspect of the present invention, a step of transmitting a short preamble sequence, a first long preamble sequence, a first signal field, and a second signal field in sequence using one of a plurality of antennas; 2) transmitting an AGC preamble using the plurality of antennas after transmitting two signal fields; and transmitting data using the plurality of antennas after transmitting the AGC preamble. The field provides a wireless transmission method having a reserve bit for notifying transmission of the AGC preamble.

  According to a seventh aspect of the present invention, a short preamble sequence, a first long preamble sequence, a first signal field and a second signal field having reserve bits transmitted sequentially from one antenna, and after the second signal field. A receiving unit that receives a signal including a plurality of AGC preambles and data signals transmitted in sequence from a plurality of antennas to generate a received signal; amplifying the received signal with a variable gain amplifier; and receiving the reserved bits And a step of controlling the gain of the variable gain amplifier using the AGC preamble as a trigger.

  According to the present invention, when receiving signals from a plurality of transmission antennas, it is possible to perform AGC with high accuracy and appropriately perform A / D conversion.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, a wireless packet including a wireless communication preamble signal according to an embodiment of the present invention is first arranged with a PLCP (Physical Layer Convergence Protocol) signal transmitted from a single antenna Tx1. The PLCP signal has a short preamble sequence 101, a first long preamble sequence 102, a first signal field (SIGNAL) 103, and a second signal field (SIGNAL 2) 104. The unit preamble SP of the short preamble sequence 101 and the unit preamble LP of the first long preamble sequence 102 are each a fixed-length signal sequence, and the length of LP is relatively larger than the length of SP.

  The short preamble sequence 101, the first long preamble sequence 102, and the first signal field 103 are compliant with the IEEE 802.11a standard. A guard interval GI is arranged between the short preamble sequence 101 and the first long preamble sequence 102. The second signal field 104 is a field necessary for IEEE 802.11n, which is a new wireless LAN standard. The first signal field 103 and the second signal field 104 will be described in detail later.

  After the PLCP signal, AGC preambles 105A to 105D that are simultaneously transmitted from a plurality of antennas Tx1 to Tx4 are arranged. AGC preambles 105 </ b> A to 105 </ b> D are used so that a signal transmitted using a plurality of transmission antennas can be demodulated with appropriate quality in a receiving apparatus. That is, the AGC preambles 105A to 105D are preambles that enable the receiving apparatus to perform optimal AGC when communicating using MIMO (Multi Input Multi Output) technology. This is a preamble that is unique to the case.

  After the AGC preambles 105A to 105D, second long preamble sequences 106A to 109A, 106B to 109B, 106C to 109C, and 106D to 109D are arranged, respectively. In the present embodiment, a case is described in which the same signal sequence is used as the AGC preambles 105A to 105D. However, the AGC preambles 105A to 105D may be different signal sequences. Guard intervals GI are arranged between the unit preambles LP forming the second long preamble sequences 106A to 109A, 106B to 109B, 106C to 109C, and 106D to 109D. As will be described later, the second long preamble sequences 106A to 109A, 106B to 109B, 106C to 109C, and 106D to 109D are orthogonalized.

  Transmission data transmitted from the antennas Tx1 to Tx4 after the above-described radio communication preamble signal, that is, after transmission of the second long preamble sequences 106A to 109A, 106B to 109B, 106C to 109C, and 106D to 109D, respectively. (DATA) 110A to 110D are arranged.

  Next, before describing the first signal field 103, the second signal field 104 will be described. In the second signal field 104, identification information indicating that the wireless packet of FIG. 1 is compatible with IEEE 802.11n, which is a standard other than the IEEE 802.11a standard, is described. In other words, the second signal field 104 indicates that the second long preamble sequences 106A to 109A, 106B to 109B, 106C to 109C, and 106D to 109D are received next, and the number of symbols of the second long preamble sequence. Further, MCS (Modulation and Coding Scheme) which is a combination of a modulation scheme (Modulation Scheme) and a coding scheme (Coding Scheme) of transmission data 110A to 110D is shown. The encoding method indicates a coding rate of a convolutional code that is an error correction code.

  Next, the first signal field 103 will be described in detail. In the first signal field 103, information indicating the modulation scheme and radio packet length of the subsequent transmission data 110A to 110D is described. As described above, the PLCP signal section, particularly the wireless packet section from the short preamble sequence 101 to the first signal field 103 among the wireless communication preamble signals shown in FIG. 1 conforms to the IEEE 802.11a standard.

  FIG. 2 shows a wireless packet including a preamble signal for wireless communication based on the IEEE 802.11a standard. A single transmission antenna Tx1 transmits a short preamble sequence x11 used for time synchronization, frequency synchronization and AGC, a long preamble sequence x12 for channel response estimation, and a signal field x13 including a field indicating the modulation scheme and length of a radio packet. Thereafter, transmission transmission data x14 and x18 are transmitted.

  The first signal field 103 in FIG. 1 is the same as the signal field x13 in the preamble signal for wireless communication based on the IEEE 802.11a standard shown in FIG. The first signal field 103 is a rate part (RATE) 131 indicating MCS of a data signal in a wireless packet based on the IEEE 802.11a standard, as shown in detail in the lower part of FIG. 1, reserved for future standard expansion Reserved bits (R) 132, a packet length part (LENGTH) 133 indicating the length of the radio packet, a parity part (P) 134 for performing parity check of information from the rate part 131 to the packet length part 133, and a convolutional code The signal tail part (SIGNAL TAIL) 135 for terminating the signal is OFDM-multiplexed and transmitted from the transmission antenna Tx1.

  Therefore, if the wireless device conforms to the IEEE 802.11a standard, a normal reception operation can be performed in the wireless packet section indicated by the packet length portion 133. That is, the wireless packet is not destroyed when another wireless transmission device compliant with the IEEE 802.11a standard starts transmission in the signal section following the first signal field 103.

  The reserve bit 132 is unnecessary and is not used in a radio device compatible with the IEEE 802.11a standard. In the embodiment of the present invention, by giving meaning to the reserve bit 132, it is possible to control the operation of a wireless device of a specific standard other than IEEE 802.11a, for example, the IEEE 802.11n standard. Specifically, the reserve bit 132 indicates that, for example, (a) AGC preambles 105A to 105D are transmitted in advance, or (b) a wireless packet corresponding to the IEEE 802.11n standard shown in FIG. 1 is transmitted. Or (c) a notice of transmission of the AGC preambles 105A to 105D and the data 110A to 110D using a plurality of transmission antennas 205A to 205D, or (d) a notice of the transmission of the second signal field 104 by the reserve bit 132 To do.

  Here, the notice in (a) includes notifying the transmission of the AGC preambles 105A to 105D indirectly by notifying the transmission of the second signal field 104 by the reserve bit 132. As shown in FIG. 1, the wireless packet corresponding to the IEEE 802.11n standard in (b) is a short preamble sequence 101, a first long preamble sequence 102, a first signal field 103, a second signal field 104, and for AGC. A wireless packet including a preamble 105A to 105D, a second long preamble sequence 106A to 109A, 106B to 109B, 106C to 109C, 106D to 109D, and data 110A to 110D, and signals from a plurality of transmission antennas using MIMO technology It is a radio packet including a multiplexed signal.

  If the reserved bit 132 is transmitted with a predetermined value, for example, “1”, the wireless device of the IEEE 802.11n standard receives and demodulates the reserved bit 132, thereby transmitting a wireless packet corresponding to the IEEE 802.11n standard. It is possible to recognize reception. Specifically, the reserve bit 132 indicates that the radio packet of FIG. 1 is received, and further indicates that the second signal field and the AGC preambles 105A to 105D are received next after the reserve bit 132. It is possible.

  Next, a wireless transmission device according to the present embodiment will be described with reference to FIG. First, the wireless communication preamble signal output from the transmission data 201 and the memory 202 is modulated by the digital modulation unit 203 to assemble a wireless packet. The assembled wireless packet is subjected to processing necessary for transmission, for example, D / A (digital-analog) conversion, frequency conversion to RF (radio frequency) band (up-conversion), and power amplification by the transmission units 204A to 204D. Thereafter, the signals are supplied to a plurality of transmission antennas 205A to 205D corresponding to the antennas Tx1 to Tx4 described in FIG. 1, and RF signals are transmitted from the transmission antennas 205A to 205D toward the radio reception apparatus shown in FIG. Hereinafter, Tx1 to Tx4 in FIG. 1 will be described as transmitting antennas 205A to 205D.

  In the present embodiment, the PLCP from the short preamble sequence 101 to the first long preamble sequence 102 shown in FIG. 1 to the first signal field 103 and the second signal field 104 including the reserve bit 132 indicating the meaning as described above. The signal is transmitted from the transmission unit 204A in FIG. 3 only by the transmission antenna 205A. The AGC preambles 105A to 105D, second long preamble sequences 106A to 109A, 106B to 109B, 106C to 109C and 106D to 109D and data 110A to 110D and the data 110A to 110D shown in FIG. 204A to 204D are transmitted by transmission antennas 205A to 205D.

  On the other hand, in the wireless reception device shown in FIG. 4, the RF signals transmitted from the wireless transmission device shown in FIG. 2 are received by the plurality of reception antennas 301A to 301D. The wireless reception device may include a single reception antenna. RF reception signals from the reception antennas 301A to 301D are input to the reception units 302A to 302D, respectively. Receiving units 302A to 302D perform reception processing, for example, frequency conversion (down-conversion) from RF band to BB (baseband) band, AGC (automatic gain control), and A / D (analog-digital) conversion, and baseband A signal is generated.

  Baseband signals from receiving sections 302A to 302D are input to transmission path estimation sections 303A to 303D and digital demodulation section 304. Transmission path estimation sections 303A to 303D estimate transmission path responses from the wireless transmission device in FIG. 3 to the wireless reception device in FIG. The transmission path estimation units 303A to 303D will be described in detail later. The digital demodulator 304 demodulates the baseband signal according to the transmission path response estimated by the transmission path estimators 303A to 303D, and generates reception data 305 corresponding to the transmission data 201 shown in FIG.

  More specifically, the digital demodulation unit 304 has a transmission line equalizer at the input unit. The transmission line equalizer performs equalization processing for removing distortion received by the received signal on the transmission line according to the estimated transmission line response. The digital demodulation unit 304 further performs demodulation processing on the equalized signal at an appropriate demodulation timing based on the above-described time synchronization processing, and reproduces data.

  Next, the receiving units 302A to 302D shown in FIG. 4 will be described. FIG. 5 shows a detailed configuration of the receiving unit 302A. Since the other receiving units 302B to 302D are the same, only the receiving unit 302A will be described here. The RF reception signal input from the reception antenna 301A is down-converted by the down converter 401, and a baseband signal is generated. In this case, the RF reception signal may be directly converted into the BB band, or may be converted into the BB band after being converted into the IF (intermediate frequency) band once.

  The baseband signal generated by the down converter 401 is input to the variable gain amplifier 402, and AGC, that is, signal level adjustment is performed. The output signal from the variable gain amplifier 402 is converted into a digital signal by the A / D converter 403. The digital signal output from the A / D converter 403 is output to the outside of the receiving unit 302A and also input to the gain control unit 404. The gain control unit 404 calculates a gain from the digital signal from the A / D converter 403, and controls the gain of the variable gain amplifier 402 based on the gain calculation. Specific contents of the AGC will be described later.

  Next, the operation of the radio reception apparatus described with reference to FIGS. 4 and 5 will be described by paying attention to the case of receiving a transmission signal of a radio packet including the radio communication preamble signal shown in FIG. First, the radio receiving apparatus receives the short preamble sequence 101 transmitted from the transmission antenna 205A in FIG. 3, and uses the baseband signal corresponding to the short preamble sequence 101 to detect frame head, time synchronization, and AFC (automatic frequency control). ) And AGC control. AFC is also called frequency synchronization. Since well-known techniques can be used for frame head detection, time synchronization, and AFC, description thereof will be omitted, and AGC will be particularly described here.

  The baseband signal corresponding to the short preamble sequence 101 is amplified by the variable gain amplifier 402 according to an initial gain value given in advance. An output signal from the variable gain amplifier 402 is input to the gain control unit 404 via the A / D converter 403. The gain control unit 404 calculates the gain from the level after A / D conversion of the received signal corresponding to the short preamble sequence 101, and controls the gain of the variable gain amplifier 402 accordingly.

  Now, let X be the level after A / D conversion of the baseband signal corresponding to the short preamble string 101. When the level X is high, the baseband signal exceeds the upper limit of the input dynamic range of the A / D converter 403, and the digital signal obtained by the A / D conversion causes saturation. For this reason, particularly high-level signals are distorted. On the other hand, when the level X is low, particularly a low level signal includes a large quantization error due to A / D conversion. As described above, whether the level X after A / D conversion is high or low, the A / D converter 403 does not perform appropriate conversion, which greatly impedes reception quality.

  In order to solve this problem, the gain control unit 404 adjusts the gain of the variable gain amplifier 402 so that the level X after A / D conversion of the baseband signal corresponding to the short preamble sequence 101 becomes the predetermined target value Z. To control. If the level of the baseband signal is so high that the signals input to the A / D converter 403 are all saturated, or vice versa, the gain of the variable gain amplifier 402 can be controlled by a single control. It may not be possible to control properly. In such a case, the gain control is repeated. As a result, the level of the baseband signal input to the A / D converter 403 can be adjusted to an appropriate level that falls within the input dynamic range of the A / D converter 403. In this way, by controlling the gain of the variable gain amplifier 402 using the baseband signal corresponding to the short preamble sequence 101, it is possible to perform appropriate A / D conversion and avoid deterioration in reception quality.

  In the above description, the reception level necessary for gain calculation for the variable gain amplifier 402 is measured using the digital signal output from the A / D converter 403. The analog signal before A / D conversion is used. It is also possible to perform level measurement using. Further, the reception level may be measured in the IF band or the RF band instead of the BB band.

  Next, the wireless reception device receives the first long preamble sequence 102 transmitted from the transmission antenna 205A, and performs transmission path estimation using the baseband signal corresponding to the long preamble sequence 102, that is, from the wireless transmission device to the wireless reception device. The transmission line response (frequency transfer characteristic) is estimated. Since the AGC has been completed for the signal transmitted from the transmitting antenna 205A as described above, the level of the input to the A / D converter 403 is appropriately adjusted when performing transmission path estimation. Therefore, for the signal transmitted from the transmitting antenna 205A, a highly accurate digital signal can be obtained from the A / D converter 403, and therefore the transmission path can be estimated accurately using this digital signal.

  Next, the wireless reception device receives the first signal field 103 transmitted from the transmission antenna 205A, and performs digital demodulation on the baseband signal corresponding to the first signal field 103 using the result of the transmission path estimation described above. The unit 404 performs demodulation processing. In the first signal field 103, as shown in FIG. 1, a rate part 131 indicating MCS of data following the preamble data and a packet length part 133 indicating the length of the radio packet are described. The wireless reception apparatus continues the demodulation process by the digital demodulation unit 404 in the wireless packet section recognized from the packet length part 133 in the first signal field 103.

  Next, the digital demodulator 304 in FIG. 4 will be described in detail with reference to FIG. The digital demodulator 304 receives the signal 500 from the receivers 302A to 302D shown in FIG. The digital demodulation unit 304 includes an FFT (Fast Fourier Transform) unit 501, a symbol timing control unit 502, a demapping unit 503, an error correction unit 504, a signal decoding unit 505, and an AGC start control unit 506.

  The symbol timing control unit 502 performs symbol synchronization, which is one of timing synchronization (time synchronization), using the input short preamble sequence 101, long preamble sequence 102, and the like. Specifically, each symbol delimiter shown in the wireless packet of FIG. 1 is recognized. Since the symbol synchronization method is a known technique, a detailed description thereof will be omitted.

  The FFT unit 501 performs FFT on the input signal 500 in accordance with the timing recognized by the symbol timing control unit 502 and performs transmission path estimation using the first long preamble sequence 102. Since transmission path estimation is also a known technique, description thereof is omitted.

  Next, the FFT unit 501 performs FFT on the input signal 500 at the timing of the first signal field 103. The output from the FFT unit 501 is converted into a binary sequence by the demapping unit 503 and then input to the error correction unit 504. The output after error correction is output as received data 305 from the digital demodulator 304 and also input to the signal decoder 505. Note that the output of the demapping unit 503 can be directly input to the signal decoding unit 505 without using error correction.

  When the signal decoding unit 505 decodes the reserved bit 132 in the first signal field 103 and detects that the value is a predetermined value, for example, “1”, it will soon receive the AGC preambles 105A to 105D. Recognize and notify the AGC start control unit 506 to that effect, that is, the AGC preamble reception notice. When receiving the AGC preamble reception advance notice, the AGC start control unit 506 sends an AGC start command to the gain control unit 404 shown in FIG. 5 and performs control to start the gain control operation.

  Next, after receiving the second signal field 104 transmitted from the transmission antenna 205A, the wireless reception apparatus receives the AGC preambles 105A to 105D transmitted from the transmission antennas 205A to 205D. The AGC preambles 105A to 105D are transmitted from the transmission antenna 205A that has continued to transmit up to the second signal field 104 and from the transmission antennas 205B to 205D that have not transmitted until now. Therefore, compared with the case where signals (first short preamble sequence 101, second long preamble sequence 102, first signal 103, and second signal 104) transmitted only from transmitting antenna 205A are received, AGC preambles 105A˜ The reception level when receiving 105D changes.

  At this time, since the AGC start control unit 506 has already received the AGC preamble reception advance notice from the signal decoding unit 505, the AGC preambles 105A to 105D are shown in FIG. 5 using the symbol timing information from the symbol timing control unit 502. An AGC start command is sent to the receiving units 302A to 302D in accordance with the time passing through the A / D converter 403 therein. Receiving sections 302A to 302D, when receiving an AGC start command, perform AGC again using AGC preambles 105A to 105D. As a result, the signal transmitted simultaneously from the transmitting antennas 205A to 205D, that is, the signal transmitted through the MIMO (Multi Input Multi Output) channel is appropriately adjusted in reception level and input to the A / D converter 403. Can do.

  A second AGC start command may be issued after the second signal field 104 is decoded, but in this embodiment, the AGC start command is issued when the reserved bit 132 of the first signal field 103 is decoded. Thereby, it is possible to provide a margin for the time from when the AGC start command is issued until the AGC is actually started. Specifically, a margin is generated for the time required for decoding the second signal field 104. Accordingly, it is possible to reduce the decoding speed and provide an inexpensive LSI as compared with the method of issuing the AGC start command after decoding the second signal field 104. In addition, compared with the method of issuing the AGC start command after decoding the second signal field 104, it is possible to increase the time during which AGC using the AGC preambles 105A to 105D can be performed. High quality reception is possible. That is, as shown in FIG. 4, the gain control for the variable gain amplifier 402 is performed again using the level after the A / D conversion of the baseband signal corresponding to the AGC preambles 105A to 105D.

  In the conventional technique, AGC is performed using only the short preamble sequence in the preamble signal transmitted from the antenna Tx1. That is, even when signals transmitted from antennas Tx2 to TX4 other than antenna Tx1 are received, AGC is performed only according to the reception level for the signals transmitted from antenna Tx1.

  FIG. 7 is a distribution diagram of received power in the short preamble and data portion when the conventional method is used. The propagation path is a multipath environment with a delay time of 50 nsec (data 1 symbol time is 4 μsec). As can be seen from this figure, it can be seen that the reception level of the short preamble x01 does not match the reception level ratio of the data portion.

  For example, in the area A in FIG. 7, the received power of the short preamble x01 is strongly received even though the received power of the data parts x08 to x11 is low. For this reason, when the AGC is adjusted based on the received power of the short preamble x01, the received power of the data portion becomes lower and a quantization error is caused in the A / D converter 403. On the other hand, in the region B in FIG. 7, the power of the short preamble x01 is received with a small power even though the received power of the data parts x08 to x11 is large. Therefore, when AGC is performed based on the received power of the short preamble x01, the data portions x08 to x11 cause saturation in the A / D converter 304. Thus, it can be seen that in the conventional method, the reception ratio of the data parts x08 to x11 and the power ratio of the short preamble are not constant, and therefore the reception characteristics are deteriorated due to the influence of quantization error and saturation.

  On the other hand, according to the present embodiment, AGC preambles 105A to 105D are transmitted from all antennas that transmit data signals. FIG. 8 shows a received power distribution diagram of the short preamble and data portion according to the present embodiment. The propagation path is the same environment as in FIG.

  As can be seen from FIG. 8, the received power of the AGC preamble and the received power of the data units 110 </ b> A to 110 </ b> D in this embodiment are in a substantially proportional relationship. Therefore, in this embodiment, even when the data 110A to 110D shown in FIG. 1 transmitted simultaneously from all the antennas Tx1 to Tx4 (transmission antennas 205A to 205D) are received, the input level to the A / D converter is Since the adjustment is appropriately performed, the influence of saturation and quantization error generated in the conventional method can be greatly reduced, so that the reception accuracy is greatly improved as compared with the conventional method.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows the radio | wireless packet containing the preamble signal according to one Embodiment of this invention Diagram showing wireless packet conforming to IEEE 802.11a 1 is a block diagram of a wireless transmission device according to an embodiment of the present invention. The block diagram of the radio | wireless receiving apparatus according to one Embodiment of this invention The block diagram which shows the specific example of the receiving part shown in FIG. Block diagram showing a specific example of the digital demodulator shown in FIG. Distribution of received power in the short preamble and data part when using the conventional method Distribution diagram of received power of short preamble and data part in one embodiment of the present invention The figure which shows the radio | wireless packet containing the preamble signal proposed by the nonpatent literature 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Short preamble sequence 102 ... 1st long preamble sequence 103 ... 1st signal field 104 ... 2nd signal field 105A-105D ... AGC preamble 106A-109A, 106B-109B, 106C-109C, 106D-109D ... 2nd long Preamble sequence 110A to 110D ... data 202 ... memory 203 ... digital modulation unit 204A-204D ... transmission unit 205A-205D ... transmission antenna 301A ... 301D ... reception antenna 302, 302A-302D ... reception unit 303A-303D ... transmission path estimation unit 304 Digital demodulator 401 Down converter 402, 402A to 402D Variable gain amplifier 403 A / D converter 404 Gain controller 501 FFT unit 502 Symbol Timing control unit 503 ... demapper 504 ... error correction section 505 ... signal decoding unit 506 ... AGC start control unit

Claims (12)

With multiple antennas;
Means for transmitting a short preamble sequence, a first long preamble sequence, a first signal field and a second signal field using one of the plurality of antennas;
Means for transmitting an AGC preamble using the plurality of antennas after transmitting the second signal field;
Means for transmitting data using the plurality of antennas after transmission of the AGC preamble, and wherein the first signal field has a reserve bit for notifying transmission of the AGC preamble. With multiple antennas;
Means for transmitting a short preamble sequence, a first long preamble sequence, a first signal field and a second signal field using one of the plurality of antennas;
Means for transmitting an AGC preamble using the plurality of antennas after transmitting the second signal field;
Means for transmitting data using the plurality of antennas after transmitting the AGC preamble, and the first signal field is a reserve bit indicating that the second signal field, the AGC preamble and data are transmitted A wireless transmission device. With multiple antennas;
Means for sequentially transmitting a short preamble sequence, a first long preamble sequence, a first signal field, and a second signal field using one of the plurality of antennas;
Means for transmitting an AGC preamble using the plurality of antennas after transmitting the second signal field;
Means for transmitting data using the plurality of antennas after transmission of the AGC preamble, and the first signal field notifies the AGC preamble and data transmission using the plurality of antennas. A wireless transmitter having a reserve bit to indicate.   4. The radio transmission according to claim 1, wherein the first signal field indicates that the short preamble sequence, the first long preamble sequence, and the first signal field are signals corresponding to the IEEE 802.11a standard. 5. apparatus.   4. The wireless transmission device according to claim 1, wherein the second signal field indicates that a signal transmitted after the second signal field is a signal corresponding to a specific standard other than IEEE 802.11a. 5. .   4. The radio transmission apparatus according to claim 1, wherein the second signal field indicates the number of the plurality of antennas and MCS (Modulation and Coding Scheme) of the data. 5.   4. The wireless communication apparatus according to claim 1, further comprising: a second long preamble sequence using at least one of the plurality of antennas after transmitting the AGC preamble and before transmitting the data. The wireless transmission device according to claim 1. A short preamble sequence transmitted in order from one antenna, a first long preamble sequence, a first signal field and a second signal field having reserved bits, and a plurality of antennas sequentially transmitted from a plurality of antennas after the second signal field A receiving unit that receives a signal including an AGC preamble and a data signal and generates a received signal;
A variable gain amplifier for amplifying the received signal;
A radio receiving apparatus comprising: a gain control unit configured to control a gain of the variable gain amplifier using the AGC preamble, triggered by reception of the reserved bits. A short preamble sequence transmitted from one antenna in sequence, a first long preamble sequence, a first signal field and a second signal field having reserved bits, and a plurality of antennas sequentially transmitted from a plurality of antennas after the second signal field A receiving unit that receives a signal including an AGC preamble and a data signal and generates a received signal;
A variable gain amplifier for amplifying the received signal;
A gain control unit for controlling the gain of the variable gain amplifier using the AGC preamble;
A radio receiving apparatus comprising: a start control unit that performs control to start a gain control operation of the gain control unit in response to reception of the reserve bit.   10. The radio reception apparatus according to claim 8, further comprising an A / D converter that converts an output signal of the variable gain amplifier into a digital signal. Transmitting a short preamble sequence, a first long preamble sequence, a first signal field, and a second signal field in order using one of a plurality of antennas;
Transmitting an AGC preamble using the plurality of antennas after transmitting the second signal field;
And transmitting data using the plurality of antennas after transmitting the AGC preamble, wherein the first signal field has a reserve bit for notifying transmission of the AGC preamble. A short preamble sequence transmitted from one antenna in sequence, a first long preamble sequence, a first signal field and a second signal field having reserved bits, and a plurality of antennas sequentially transmitted from a plurality of antennas after the second signal field A receiving unit that receives a signal including an AGC preamble and a data signal and generates a received signal;
Amplifying the received signal with a variable gain amplifier;
And a step of controlling the gain of the variable gain amplifier using the AGC preamble, triggered by reception of the reserved bits.

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